Section Articles

Neck rot of onions and garlic

The causative agent of this most common and harmful disease of onions and garlic is a fungus. Botrytis allii Munn.

Onion neck rotOnion neck rot

Primary infection of plants occurs in the field even before harvesting when the leaves are lodged, which is a favorable substrate for the development of the fungus. The causative agent of cervical rot penetrates into tissues through a loosely closed neck and mechanical damage. Infection in the initial period is not detected, therefore, the affected bulbs, along with healthy ones, enter the storage. The first symptoms of the disease become noticeable already at the beginning of storage (September – October). Rot of the neck develops as a result of infection in the field and rot of the side parts or bottom due to re-infection from nearby diseased bulbs. The bulb softens in the affected area, the tissue becomes watery, yellow-pink in color, with an unpleasant odor. When all scales are damaged, the bulbs are mummified. On the surface of the affected scales, a dense gray mold is formed, which is a mass of conidiophores of the fungus and colorless, oval, unicellular conidia 7-16x4-9 microns in size. Later, sclerotia of the fungus appears among the mold, often merging into a solid black crust.

The intensity of the manifestation of cervical rot depends on many environmental factors. The rapid development of the disease in the storage facility is facilitated by high humidity and temperature. The optimum temperature for the fungus is 20 ° C, but it can develop even at 3-4 ° C. The growth and development of the pathogen stops only at 0 ° C.

Garlic neck rotGarlic neck rot

Seed bulbs are the main source of infection in onion culture from sets. When they are planted in the field, the causative agent of the disease can affect the arrows and seed heads. The arrows break, the seeds are underdeveloped, and have poor germination. The infection formed on the testes is transferred to the turnip, where it gets to the lower dying leaves, and then to the bulb, causing it to become infected. When onion is cultivated from seeds, the plant becomes infected mainly from the crops of turnip and testes. The role of soil as a source of infection is less significant. In it, mainly sclerotia of the fungus can be preserved. There is the possibility of spreading the disease with the seeds, since the causative agent of cervical rot is capable of infecting the seed heads.

The development of the disease is greatly influenced by the conditions for growing onions. In the same weather, onions are more strongly affected on loamy soils; weaker - on sandy loam. Higher soil moisture creates favorable conditions for the fungus. In addition, the duration of the growing season of plants is lengthened, the ripening of the bulbs slows down, and the leaves dry out more slowly.

Increased doses of nitrogen, violation of the timing of harvesting and the conditions of post-harvest drying contribute to increased damage to onions. Harvesting unripe bulbs and storing them without sufficient drying dramatically increases the bulbs' susceptibility to neck rot.

Measures to combat cervical rot

To reduce the loss of onions from neck rot, first of all, it is necessary to obtain healthy planting material. To do this, black onions should be sown in separate areas, remote from the fields occupied by turnip onions and seed plants. Harvesting of the bulbs should be carried out during their full ripening, followed by drying the bulbs in sunny weather in an open place in one layer, in a humid one - first under a canopy, and then for 7-10 days indoors with the air heated to 26-35 ° C. When pruning onions, leave a neck 3–6 cm long. It is recommended to store onions under optimal conditions: food - at a temperature of 1–3 ° С and relative humidity of 75–80%, uterine bulbs - at 2–5 ° С and 70–80% , sowing - at 18–20 ° С and 60–70%.

When pickling onions and garlic against cervical rot, it is allowed to use the following fungicides: "Benlat" ("Fundazol") - 0.7% suspension (immersion of the bulbs in the suspension of the preparation for 20 minutes before laying for storage, followed by drying), or "Tigam »- 3-4 kg / t (seed treatment, seed dressing), or TMTD - 4-5 kg ​​/ t for seed dressing and 2-3% suspension for seed dressing.

Currently, no varieties of onions resistant to this disease have been identified. The varieties Mstersky local, Danilevsky 301, Bessonovsky local are less affected. Varshavsky, Pogarsky, Tsitaussky and varieties with dark-colored scales. Early ripening onion varieties are less susceptible to neck rot.

"Ural gardener" No. 3-2014

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